= A hydrogen atom (m - 1.674 x 10-27 kg) is moving with a velocity of 1.1250 x 107 m/s. It collides elastically with a helium atom (m= 6.646 x 10-27 kg) at rest. After the collision, the hydrogen atom is found to be moving with a velocity of -6.724 × 106 m/s (in a direction opposite to its original motion). Find the velocity of the helium atom after the collision in two different ways: (a) by applying conservation of momentum; (b) by applying conservation of energy.

= A hydrogen atom (m - 1.674 x 10-27 kg) is moving with a velocity of 1.1250 x 107 m/s. It collides elastically with a helium atom (m= 6.646 x 10-27 kg) at rest. After the collision, the hydrogen atom is found to be moving with a velocity of -6.724 × 106 m/s (in a direction opposite to its original motion). Find the velocity of the helium atom after the collision in two different ways: (a) by applying conservation of momentum; (b) by applying conservation of energy.